03-13-2014, 07:05 PM
Yes, it appears that the problem is that the transistor is not conducting enough to fully turn on the LED. Don't worry about grounding the MPX connection. You are only doing what the transistor should do and it will not cause any damage.
The spark is caused by the charged 100 uF cap being discharged to ground. You can put the 68 ohm resistor in series with the cliplead to limit the spark.
How much does the voltage at the collector change when receiving stereo? It should go from about 24 to almost zero, so if it is not then either the transistor is bad or it is not getting enough drive from the MPX circuit.
The spark is caused by the charged 100 uF cap being discharged to ground. You can put the 68 ohm resistor in series with the cliplead to limit the spark.
How much does the voltage at the collector change when receiving stereo? It should go from about 24 to almost zero, so if it is not then either the transistor is bad or it is not getting enough drive from the MPX circuit.
